Went into CEX high Wycombe yesterday as I was looking for a 360 for my girlfriends younger sister and came across this.
They are currently selling Pre-owned Xbox 360's with 20Gb hard drive, wireless controller PSU, AV cable (composite connections only on the cable) with a game from a selection for only £90. There were about 6/7 games which included MW2 GTA4 and Bioshock 2. Also comes with a year warranty.
The console I bought had an MFR date of July 2008 and had an HDMI port on the back.
Sorry I don't know if this is nationwide.
it may also be an idea if your interested to ask them how much it extra it would cost for a 60GB instead of the 20GB as they only charged me £93 (I think they mis-quoted me as it was supposed to be £98 when they brought it up on their till).